This invention relates in general to a device for translating linear reciprocating motion to rotary motion, and vice versa, and particularly to an engine or a pump employing a gear driven crankshaft.
Internal combustion engines normally have at least one piston that is reciprocated within a cylinder. A rod connects the piston to a crankshaft which has offset portions that cause the end of the rod to orbit about an axis of the crankshaft. The rotation of the crankshaft drives a transmission. Piston pumps operate in a similar manner, using a rotatably driven crankshaft to drive the pistons. While crankshafts of this nature are certainly workable, there are limitations. One limitation is that since the second end of the rod orbits, only one side of the cylinder can be utilized as a working fluid chamber. Also, the length of the stroke is fixed for a given crankshaft. Changing the length of the stroke will change the torque, however requires replacing the crankshaft.
The driver apparatus of this invention, whether utilized as an engine or pump, has a piston slidably carrying in a cylinder for stroking reciprocally along an axis of the cylinder. A piston rod connects to the piston and has a second end that connects to a power gear. The power gear is concentrically mounted to a power gear shaft and has a link pin connected between the second end of the piston rod and the power gear. The point of connection of the link pin is offset from the power gear axis so that as the second end of the rod strokes, the power gear rotates.
The power gear engages teeth of a rim gear, which when held stationary, causes the power gear to orbit about the rim gear as the power gear rotates. A crankshaft gear is concentrically mounted to a primary shaft for rotation with it. The power gear shaft engages the crankshaft gear at a point offset from the primary shaft so that as the primary gear orbits about the rim gear, the crankshaft gear and the primary shaft will rotate.
The pitch diameter of the rim gear is a multiple of the pitch diameter of the power gear. By positioning the link pin axis on the pitch diameter of the power gear, the second end of the rod can be constrained to travel the along of the axis of the cylinder. The cylinder can thus have a second head with a sealed aperture through which the rod sealingly passes. The second head defines a second working chamber, which can be used to pump a liquid, compress gas, or serve as another combustion chamber. For example, the second working fluid chamber can be used to pre-compress a fuel and air mixture in an accumulator, then on a subsequent stroke, deliver the mixture to the first working fluid chamber for combustion.
If the axis of the link pin is positioned at a point between the pitch diameter of the rim gear and the axis of the rim gear, it will cause the second rod end to rotate about an elliptical path. The elliptical path can be designed to achieve the desired rate of speed of the piston within the cylinder at various points along the stroke.
The rim gear can be rotated from a maximum stroke position to a minimum stroke position. In the maximum stroke position, the link pin located is on the cylinder axis, and the rod is aligned with the cylinder axis, while the link pin is closest to and farthest from the center point or axis of the rim gear. In the minimum stroke position, the rim gear is rotated 90xc2x0 from the maximum stroke position. This places the power gear farthest from the center point of the rim gear when it is located at 90xc2x0 and 270xc2x0 positions on the rim gear relative to the cylinder axis. Shifting the rim gear toward the minimum stroke position reduces the length of the stroke but increases the torque.
The rotation of the rim gear can be performed manually or by a separate actuator. Also, the rim gear may be allowed to move in response to a pressure increase when the device operates as a pump or compressor. As the pressure increases, the rim gear will naturally rotate so as to decrease the stroke length and increase the torque. A spring or other type of actuator can be connected to the rim gear to urge it toward the maximum stroke position.